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13 Replies

Without seeing your pcell, who knows what the problem is. Most likely there is a difference between what the pcell is expecting and what the CDF value is - either in the type of the value it sees, or in the value. Maybe the pcell is expecting the value to be in microns?

Above you seem to be setting the default value in the first case to 0.2 nm (which is a bit small and rather ahead of state of the art technology).

The type of the pcell parameters is float, but the type in the CDF is string - so you have a mismatch. They need to be consistent, and ideally the default values should be consistent. In this case you have the w in the pcell in microns, but the CDF in metres. Consistency is the key.

You could define the default values in the pcell as also being strings, and then use something cdfParseFloatString() in the pcell code to convert to a number, and do whatever scaling you need.

My guess is that your schematic has the components instantiated with values such as "0.2u" - and so with the scaling lines in the pcell, it correctly transforms it into layout units (microns).

When you're instantiating in the layout directly, and picking the value as the default (0.2), then that scaling would result in a transistor width of 20cm - which is a tad large.

So it's a units mismatch problem - you need to decide what values you want the user to enter, and then be consistent about it. Maybe your pcell default and CDF default should be "0.2u" and then you will need the scaling in the pcell to convert into microns since the layout will be drawn in microns.

Yes, Andrew, I'm aware that its a units issue. I've tried quite a few different units trying to get them to match. I get the code working one way and then it breaks another way.

For something as easy to mess up as this, it would be nice if CD not only had an example like the 90nm sample code but also an explanation of why each cb, cdf, il and symbol has to be what it is and why. Where the conversion should be etc. I've thought I had ever line matched up with the CDS examples and yet it still didn't work.

So now its just going to ahve to be skill code that is placed. Its easy to make that work. No gen from source in this version.

There is ABSOLUTELY NO REASON why you should not be able to make it work for both scenarios. Once you've decided whether the user will be setting the dimensions in metres or microns on the component, you can make it consistent everywhere.It would be very odd if you specified the dimensions differently when placing an instance on the schematic from placing an instance on the layout.

This is not complicated - so I'm slightly mystified as to why it is seen as being complicated.

Would you like to create a Service Request to get support directly from a Cadence engineer? This would likely give you better support than the online forum, especially if you have reached a point of frustration...

I had a service requite on this going as well .... after a couple of rounds they said theyweren't suppose to program for me. I just wanted them to explain why things were matching etc. tech said maybe I should look into paying for some help. But noone hear is willing to pay it seems.

I kept pluggin along. Seem to get things working, then somethings breaks. Been around block 2 or 3 times by now.

Maybe I'll create an other service request and ask for someone who know this stuff. The guy I had didn't seem to reall know the details about this issue.

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